JP4284438B2 - Deposition method - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a technical field of a film forming method, and more particularly to a method of forming a carbon nanotube.
[0002]
[Prior art]
In recent years, carbon nanotubes have attracted attention as materials for electron emission sources used in field emission displays (FEDs) and fillers for secondary batteries.
A conventional carbon nanotube film forming method will be described below.
[0003]
Reference numeral 101 in FIG. 4 shows a conventional carbon nanotube film forming apparatus. The film forming apparatus 101 has a vacuum chamber 111. An exhaust system 112 is disposed outside the vacuum chamber 111, and is configured such that when the exhaust system 112 is activated, the inside of the vacuum chamber 111 can be evacuated. Further, a gas introduction system 113 is arranged outside the vacuum chamber 111, and is configured such that when the gas introduction system 113 is activated, a source gas to be described later can be introduced into the vacuum chamber 111.
[0004]
A hole is provided in the inner bottom surface of the vacuum chamber 111, and a hollow cylindrical insulating material 115 is vertically disposed in the hole. A current introduction terminal 114 is vertically inserted into the hollow of the insulating material 115. A sample stage 116 made of a metal plate is fixed to the upper end portion of the current introduction terminal 115. On the other hand, the lower end portion of the current introduction terminal 115 is drawn out of the vacuum chamber 111. A DC power source 129 is disposed outside the vacuum chamber 111, and a lower end portion of the current introduction terminal 115 drawn out of the vacuum chamber 111 is connected to the DC power source 129.
[0005]
The vacuum chamber 111 is grounded, and the current introduction terminal 114 is insulated from the vacuum chamber 111 by the insulating material 115. When the DC power supply 129 is activated, a negative DC voltage is applied to the current introduction terminal 114, and the current introduction terminal 114 and A negative DC voltage is also applied to the sample stage 116 having the same potential.
[0006]
A through hole is provided on the ceiling side of the vacuum chamber 111, and a quartz plate 118 is disposed on the through hole. A waveguide 119 is provided on the quartz plate 118. One end of the waveguide 119 is connected to the quartz plate 118 so as to cover the entire through hole and the quartz plate 118, and the microwave generator 121 is connected to the other end of the waveguide 119. When the generator 121 is activated, microwaves are generated, and the microwaves are introduced from the waveguide 119 into the vacuum chamber 111 through the quartz plate 118.
[0007]
A film forming method for forming a carbon nanotube on a glass substrate using the film forming apparatus 101 described above will be described below. When a glass substrate is used in this manner, carbon nanotubes do not grow directly on the surface of the glass substrate. Therefore, a thin film of a material (hereinafter referred to as catalyst material) on which carbon nanotubes are grown by vapor deposition or the like in advance. A film is formed on the surface of the substrate.
[0008]
First, the exhaust system 112 is activated to evacuate the inside of the vacuum chamber 111, and the substrate described above is carried into the vacuum chamber 111 while being maintained in the vacuum state, and placed on the sample stage 116. Reference numeral 117 in FIG. 4 shows the substrate.
[0009]
Next, the gas introduction system 113 is activated, and a raw material gas that is a mixed gas of methane gas and hydrogen gas is introduced into the vacuum chamber 111 so that the pressure inside the vacuum chamber 111 becomes about 266 Pa (2 Torr).
[0010]
Next, the microwave generator 121 is activated, and the microwave is introduced into the vacuum chamber 111 through the quartz plate 118 and the through hole. The quartz plate 118 and the through hole are formed to be larger than the size of the substrate 117, and the microwave is uniformly applied to the entire surface of the substrate 117. Then, methane gas and hydrogen gas near the substrate surface are ionized by the microwave, and plasma is generated inside the vacuum chamber 111. When the plasma is generated, the DC power source 129 is activated and a negative DC voltage is applied to the sample stage 116. Then, carbon atoms in methane gas adhere to the surface of the thin film of the catalyst material formed on the surface of the substrate 117, and carbon nanotubes grow on the surface of the thin film of the catalyst material. When a desired amount of carbon nanotubes is obtained, the DC power source 129 and the gas introduction system 113 are stopped to complete the growth. In this way, carbon nanotubes can be obtained.
[0011]
However, in order to form a carbon nanotube on a large area substrate by the conventional film formation method, it is necessary to uniformly irradiate microwaves on the entire surface of the large area substrate. For this purpose, a large through hole as large as the size of the substrate is provided on the ceiling side of the vacuum chamber 111, a quartz plate 118 larger than the through hole is provided thereon, and a thick waveguide covering the entire quartz plate 118. 119 had to be provided.
[0012]
Further, the quartz plate 118 is easily contaminated by methane gas plasma. When the quartz plate 118 is contaminated, microwaves are not sufficiently introduced into the vacuum chamber 111, and in a severe case, a problem arises that carbon nanotubes are not formed on the substrate surface.
[0013]
[Problems to be solved by the invention]
The present invention was created to solve the above-described disadvantages of the prior art, and an object thereof is to form a carbon nanotube on a large-area substrate.
[0014]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the invention according to claim 1 uses a vacuum chamber, an electrode disposed in the vacuum chamber, and a substrate holder disposed in the vacuum chamber facing the electrode. Then, a catalyst material or a substrate provided with a catalyst material is held by the substrate holder, a source gas containing carbon atoms is introduced into the vacuum chamber in a vacuum atmosphere, and carbon nanotubes are formed on the surface of the substrate In the film forming method, the source gas is introduced into the vacuum chamber so that the inside of the vacuum chamber has a source gas atmosphere of 1000 Pa or more and atmospheric pressure, and the inside of the vacuum chamber in the source gas atmosphere is In this film forming method, a negative voltage having a peak voltage of −500 V and a positive voltage having a peak voltage of 1 kV are alternately applied between the electrode and the substrate holder at a frequency of 5 kHz or more .
A second aspect of the present invention is the film forming method according to the first aspect, wherein the source gas is a mixed gas of methane gas and hydrogen gas.
[0015]
According to the film forming method of the present invention, an alternating voltage is applied between the electrode and the substrate holder in a source gas atmosphere.
[0016]
When the inside of the vacuum chamber is made a source gas atmosphere and an AC voltage is applied between the electrode and the substrate holder in the source gas atmosphere, a glow discharge is generated between the electrode and the substrate holder, and the source gas is ionized to form a film. Carbon nanotubes can be grown on the resulting thin film of catalyst material.
[0017]
In addition, glow discharge generated by applying an AC voltage between the electrode and the substrate holder in the source gas atmosphere is generated between the electrode and the substrate holder. If the area of the electrode and the substrate holder is made larger than the substrate, the substrate Carbon nanotubes can be formed on the entire surface of the film. Therefore, even when a film is formed on a large-area substrate, a carbon nanotube can be easily formed on a large-area substrate by using an electrode and a substrate holder larger than the large-area substrate area. Unlike conventional methods in which carbon nanotubes are formed using a glass, carbon nanotubes can be easily formed on the substrate surface of a large area without enlarging the through-hole and quartz plate of the vacuum chamber and increasing the diameter of the waveguide. Can be membrane.
[0018]
In addition, since the quartz plate that was necessary in the past is not required, even if the plasma of the source gas is generated, the quartz plate is contaminated as in the past, and the growth of the carbon nanotubes is hindered due to the contamination. Nor.
[0019]
In the present invention, the vacuum chamber may be grounded. With this configuration, voltages having opposite polarities can be applied to the electrode and the substrate holder.
[0020]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below with reference to the drawings.
Reference numeral 1 in FIG. 1 shows a film forming apparatus used in a film forming method according to an embodiment of the present invention.
The film forming apparatus 1 has a vacuum chamber 11. An exhaust system 12 disposed outside the vacuum chamber 11 is connected to the vacuum chamber 11, and the interior of the vacuum chamber 11 can be evacuated when the exhaust system 12 is activated.
[0021]
A gas introduction system 13 is disposed outside the vacuum chamber 11. The gas introduction system 13 has three gas cylinders 53 _{1 to} 53 ₃ , and the gas cylinders 53 _{1 to} 53 ₃ are connected to the vacuum chamber 11 by piping. In each gas cylinder 53 _{1 to} 53 ₃ , methane gas, hydrogen gas, and argon gas are put, respectively, and mass flow controllers 52 _{1 to} 52 ₃ are provided in the middle of the piping. The flow rate is adjusted by the mass flow controllers 52 _{1 to} 52 ₃ and then introduced into the vacuum chamber 11.
[0022]
A mounting table 15 is provided on the inner bottom surface of the vacuum chamber 11. A sample stage 16 which is an example of a substrate holder of the present invention is disposed on the surface of the mounting table 15. The mounting table 15 is made of an insulating material, and the sample stage 16 is insulated from the vacuum chamber 11 by the mounting table 15. The surface of the sample stage 16 is flat, and a substrate to be described later can be placed on the surface.
[0023]
A heater 21 is disposed inside the mounting table 15. A heater power source 22 disposed outside the vacuum chamber 11 is connected to the heater 21. When the heater power source 22 is activated and the heater 21 is energized, the heater 21 generates heat and the sample stage 16 can be heated. It has become.
[0024]
On the inner ceiling side of the vacuum chamber 11, an electrode plate 18 is disposed facing the sample stage 16 while being insulated from the vacuum chamber 11.
[0025]
An AC pulse power source 25 is disposed outside the vacuum chamber 11, and the electrode 18 and the sample stage 16 are connected to the AC pulse power source 25. The vacuum chamber 11 is grounded, and the electrode 18 and the sample stage 16 are both insulated from the vacuum chamber 11 as described above. When the AC pulse power supply 25 is activated, a voltage is applied to the electrode 18 and the sample stage 16, respectively. It is comprised so that it can apply.
[0026]
A process for forming a carbon nanotube on a substrate provided with nickel as a catalyst material will be described.
First, the inside of the vacuum chamber 11 is evacuated by the exhaust system 12, and the pressure in the vacuum chamber 11 is reduced. When the pressure inside the vacuum chamber 11 reaches a predetermined pressure, the gas introduction system 13 is started and a mixed gas of methane gas and hydrogen gas is introduced into the vacuum chamber 11 as a raw material gas. Here, when the inside of the vacuum chamber 11 reaches 1.33 × 10 ⁻² Pa (1 × 10 ⁻⁴ Torr), methane gas and hydrogen gas are introduced by 50 sccm and 70 sccm, respectively.
[0027]
When the source gas is thus introduced and the pressure inside the vacuum chamber 11 becomes a pressure suitable for film formation, the heater 21 is energized to raise the temperature of the sample stage 16, and the temperature of the substrate 17 is brought to a temperature suitable for film formation. Raise the temperature. Here, a pressure suitable for film formation is about 1000 Pa (7.5 Torr), and a temperature suitable for film formation is about 500 ° C.
In this state, the AC pulse power supply 25 is activated, and voltages are applied to the sample stage 16 and the electrode 18, respectively.
[0028]
FIG. 2 shows a timing chart of the voltage V _s applied from the AC pulse power supply 25 to the electrode 18. The sample stage 16 is grounded. A negative voltage and a positive voltage are alternately applied to the electrode 18 at predetermined times t ₁ and t ₂ . Here, the positive peak voltage V _S1 is +1 kV, the average voltage V _S2 is +700 V, the negative peak voltage V _S4 is −500 V, and the average voltage V _S3 is −350 V. Both t ₁ and t ₂ are 1 μs, and t _f is 100 μs.
[0029]
As a result, voltages having opposite polarities are alternately applied to the sample stage 16 and the electrode 18, a glow discharge is generated between the sample stage 16 and the electrode 18, and the mixed gas of the source gas is ionized by the glow discharge. . When carbon atoms in the ionized source gas adhere to the surface of the catalyst material on the substrate 17, carbon nanotubes begin to grow on the surface of the catalyst material. At this time, the glow discharge is generated between the sample stage 16 and the electrode 18, the area of the sample stage 16 and the electrode 18 is made larger than the area of the substrate 17, and the glow discharge is generated on the entire surface of the substrate 17. Thus, carbon nanotubes begin to grow on the entire surface of the substrate 17. When about 45 minutes have elapsed from the start of growth, the introduction of the raw material gas is stopped and the growth of the carbon nanotubes is terminated. As described above, a carbon nanotube can be formed. FIG. 3 shows an SEM photograph of carbon nanotubes grown by this method.
[0030]
As described above, according to the film forming method of the present invention, a source gas, which is a mixed gas of methane gas and hydrogen gas, is introduced into a vacuum chamber in a vacuum atmosphere between the electrode and the substrate holder. An AC voltage is applied to cause glow discharge inside the vacuum chamber, and carbon nanotubes are grown on the substrate.
[0031]
As described above, if the area of the electrode 18 and the sample stage 16 is larger than the area of the substrate 17, carbon nanotubes can be formed on the entire surface of the substrate 17. Even when the film is formed, the area of the electrode 18 and the sample stage 16 may be made larger than the area of the large substrate. Therefore, unlike the conventional case where the carbon nanotube is formed using microwaves, it is not necessary to enlarge the through hole and the quartz plate of the vacuum chamber or increase the diameter of the waveguide.
[0032]
Further, since the quartz plate is not required unlike the conventional film forming apparatus, the quartz plate is not contaminated, and the growth of carbon nanotubes is not hindered due to the contamination.
[0033]
Furthermore, since the sample stage 16 can be grounded to the ground potential, the operability of the sample stage 16 such as heating and rotation is improved.
[0034]
The substrate may be made of a carbon nanotube catalyst material such as nickel.
[0035]
Further, in the embodiment described above, the pressure inside the vacuum chamber 11 when growing the carbon nanotubes is set to 1000 Pa (7.5 Torr), but the inside of the vacuum chamber 11 according to the present invention when growing the carbon nanotubes. The pressure is not limited to this, and carbon nanotubes can be grown in the range of 1000 Pa (7.5 Torr) to atmospheric pressure.
[0036]
Further, when the heater 21 is energized to raise the temperature of the substrate 17, the temperature of the substrate 17 is set to about 500 ° C., but the temperature of the substrate 17 is not limited to this, and 500 ° C. or more and 700 ° C. It may be in the range of ℃ or less _.
Further, the peak voltage of the AC pulse voltage applied to the electrode 18 is set to +1 kV and −500 V, the positive / negative voltage switching time t _{f is set} to 100 μs, and the positive and negative voltage application times t ₁ and t ₂ are both set to 1 μs. However, the switching time t _f may be 100 μs or less, and the application times t ₁ and t ₂ may be extended within a range not exceeding t _f .
[0037]
In the above-described embodiment, nickel is used as a catalyst material for carbon nanotubes. However, the catalyst material of the present invention is not limited to this, and any material that can grow carbon nanotubes on the surface may be used. Or permalloy or stainless steel.
[0038]
【The invention's effect】
Carbon nanotubes can be formed on a large-area substrate.
[Brief description of the drawings]
FIG. 1 is a diagram illustrating a configuration of a film forming apparatus used in a film forming method of the present invention. FIG. 2 is a voltage illustrating an example of a voltage applied to a substrate holder in a thin film forming method according to an embodiment of the present invention. Waveform diagram [FIG. 3] (a), (b): SEM photograph of carbon nanotubes grown by the film-forming method of the present invention [FIG. 4] A diagram for explaining a conventional film-forming apparatus using microwaves Explanation of]
DESCRIPTION OF SYMBOLS 1 ... Film-forming apparatus 11 ... Vacuum chamber 12 ... Exhaust system 13 ... Gas introduction system 16 ... Sample stage (substrate holder) 17 ... Substrate 18 ... Electrode 25 ... AC pulse power supply

Claims (2)

Using a vacuum chamber, an electrode disposed in the vacuum chamber, and a substrate holder disposed in the vacuum chamber facing the electrode,
A catalyst material or a substrate provided with a catalyst material is held by the substrate holder, a source gas containing carbon atoms is introduced into the vacuum chamber in a vacuum atmosphere, and carbon nanotubes are formed on the surface of the substrate A film forming method comprising:
Introducing the source gas into the vacuum chamber to make the inside of the vacuum chamber a source gas atmosphere of 1000 Pa or more and atmospheric pressure,
A negative voltage with a peak voltage of −500 V and a positive voltage with a peak voltage of 1 kV are alternately applied at a frequency of 5 kHz or more between the electrode and the substrate holder inside the vacuum chamber in the source gas atmosphere. Film forming method.   The film forming method according to claim 1, wherein the source gas is a mixed gas of methane gas and hydrogen gas.

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